anatomy and physiology i protein synthesis and the genetic code instructor: mary holman
TRANSCRIPT
Anatomy and Physiology I
Protein Synthesis and the
Genetic Code
Instructor: Mary Holman
Proteins• Every cell contains large numbers of
diverse proteins
• The proteins determine the physical and chemical characteristics of cells
• Much of cellular machinery is devoted to synthesizing proteins
• Instructions for making proteins are contained primarily in the DNA in the nucleus of the cell
Organic CompoundsProteins
• More complex than carbohydrates and lipids • Have a larger range of functions :
structural material, energy source, hormones, receptors, enzymes,antibodies
• Contain N as well as C, H, and O and some contain S• Amino acids are the building blocks (monomers)
of proteins• There are twenty (20) different amino acids• Amino acids bind together by forming peptide bonds
Fig. 2.17aH N
H
C
H
C
O
OH
R
The portion common to all amino acidsis within the oval.
It includes the amino group (—NH2)and the carboxyl group (—COOH).
The "R" group, or the "rest of the molecule,"is what makes each amino acid unique.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
General structure of an amino acid
Fig. 2.17b
S
C
H
HH
H N
H
C
H
C
O
OH
C
C
C
H
H
C H
C H
H
CH
CH
H N
H
C
H
C
O
OH
(b) Cysteine. Cysteine has anR group that contains sulfur.
Phenylalanine. Phenylalaninehas a complex R group.Improper metabolism ofphenylalanine occurs in thedisease phenylketonuria.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 2.18
O
OHCNCCN C
ROHH
HHHR
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
A Peptide Bond
(H2O)
Fig. 2.19a
Amino acids
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Primary Structure of Proteins
Polypeptide chain
Pleatedstructure
Coiledstructure
N
N
N
NN
HH
HH
C
CC
C
OCC
C
CC
OC
O
H
NN
H
O
O
C
CC
C
N
NHO
CC
H OC
H
R
H
R
R
H
R
H
R
H
R
H
R
H
R
H
CH
CH
Secondary Structure
Three-dimensional folding
Tertiary Structure
Quaternary Structure
Two or more folded chains may connect and fold together
Ex:Hemoglobin molecule
Nucleic Acids
• Huge molecules that contain C, H, O, N and P• Building blocks (monomers ) are nucleotides• Nucleic acids are of two varieties
• Deoxyribonucleic acid (DNA)• Ribonucleic acid (RNA)
Sugar
P Base
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Basic Structure of a NucleotideFig. 2.20
OH
HH
HOCH2
H
C C
O
HC C
H
HH
HOCH2 OH
H
C C
O
HC
OH
C
Ribose Deoxyribose
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 2.22
Different sugar groups of DNA and RNA
Nitrogenous Bases• The two types of nitrogenous
bases in nucleotides:
• Purines - structure of two joined organic rings
• Pyrimidines - have a single organic ring
Nitrogenous bases of DNA
DNA RNA
App. D Pg. 937
The Five Nitrogenous Bases
The Molecular Structure of DNAApp. D pg 937
Fig. 4.19a
G C
G
G
A
T
C
C
A
P
G C P
TP
P
C G
P
G
P
C P
A
P
P
P
Thymine (T)
Cytosine (C)
Adenine (A)
Guanine (G)
Nucleotide strand
Segmentof DNAmolecule
(a)
G C
G
G
A
T
C
C
A
P
G C P
TP
P
C G
P
G
P
C P
A
P
P
P
Thymine (T)
Cytosine (C)
Adenine (A)
Guanine (G)
Hydrogenbonds
Nucleotide strand
Segmentof DNAmolecule
Fig. 4.19a
DNA
Fig. 4.19b
Globularhistoneproteins
Chromatin
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 4.19b The Double Helix Structure of DNA
Fig. 4.19c
Metaphasechromosome
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
DNA as condensed Chromosome during Mitosis
Fig. 4.20b
C
C
A T
C
C G
G
C
C
G
CG
A
A
T
T
C G
C
A T
Newly formedDNA molecules
Region ofreplication
Original DNAmolecule
G
G
G
G
G
G
GG
G
C C
C
C
C G
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
DNA Replication prior to MitosisFig 4.20 (partial)
S
P
S
P
S
P
S
P
S
P
S
P
B
B
B
B
B
B
S
P
S
P
S
P
S
P
S
P
S
P
B
B
B
B
B
B
S
S
S
S
S
S
P
P
P
P
P
P
B
B
B
B
B
B
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 2.21
RNA DNA
Fig. 4.21
SC
S
S
S
S
G
G
G
U
A
U
U
P
P
P
P
S
S
S
SA
P
P
US
P
P
P
PRNA Differences from DNA
• RNA is single stranded• contains ribose instead
of deoxyribose• contains uracil instead
of thymine• there are different types of RNA - all with unique roles
Steps in Relaying the Genetic InformationStored in DNA to Proteins to be
Synthesized• Transcription - in nucleus
mRNA copies the DNA sequence
• mRNA enters cytoplasm and arrives at a ribosome
• Translation - on ribosome in cytoplasmtRNA matches its anticodon to codons on mRNA and delivers the corresponding amino acid.
• The polypeptide chain of a new protein is assembled on the ribosome
Fig. 4.22
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
DNA mRNA
SG
SC
S
S
S
S
C
G
T
A
S
S
S
S
G
C
A
U
Dir
ecti
on
of
“rea
din
g”
cod
e
P
P
P
P
P
P
P
P
P
P
Transcription by RNA from DNA bases
Fig. 4.23a
1
2
CytoplasmDNAdoublehelix Nucleus
MessengerRNA
AT
A
A
T
T
T
A T
A T
A T
A T
A T
U A
U A
U A
G C
C
G C
G C
G C
G C
G C
G C
G
G
C
C
G C
C G
U AC GC
G
G
GG
G
G
G
G
G
G
C
CC
C
C
C
C
C
C
C
A
A
A
A
A
T
T A
A T
A T
A T
A T
C G
G C
G C
G C
T A
T A
T A
C G
A T
G C
T A
C G
T A
C G
C G
G C
A T
T A
C G
G C
T
T
G
C G
C G
C G
C G
C G
C G
C G
C G
DNAstrandspulledapart
MessengerRNA
DNAinformationis copied, ortranscribed,into mRNAfollowingcomplementarybase pairing
Nuclearpore
mRNA leavesthe nucleusand attachesto a ribosome
Transcription (in nucleus)
DNAstrand
G C
C G
A
G
G
C
U
C
T
C
C
G
A
G
Transcription
1
2
Fig. 4.23b
mRNA leavesthe nucleusand attachesto a ribosome
Translation begins as tRNA anticodonsrecognize complementary mRNA codons,thus bringing the correct amino acids intoposition on the growing polypeptide chain
As the ribosomemoves along themRNA, more aminoacids are added
At the end of the mRNA,the ribosome releasesthe new protein
tRNA moleculescan pick up anothermolecule of thesame amino acidand be reused
Polypeptidechain
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
3
2
4
5
6
Amino acidsattached to tRNA
Fig 4.23bTranslation
Cytoplasm
Fig. 4.24a
MessengerRNA
TransferRNA
Next amino acid
Anticodon
Codons
Growingpolypeptidechain
1
1
2
2
3
3
4
4
5
5
6
6
7
CU G C G U
UCG GA AA A A AG G G G G G G GC C C C C C CU U
The transfer RNA moleculefor the last amino acid addedholds the growing polypeptidechain and is attached to itscomplementary codon on mRNA.
1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 4.24b
MessengerRNA
TransferRNA
Next amino acid
Anticodon
Codons
1
1
2
2
3
3
4
4
5
5
6
6
7
CU G C G U
Peptide bond
UCG GA AA A A AG G G G G G G GC C C C C C CU U
2A second tRNA bindscomplementarily to thenext codon, and in doingso brings the next aminoacid into position on the ribosome.A peptide bond forms, linkingthe new amino acid to thegrowing polypeptide chain.
Growingpolypeptidechain
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 4.24c
CU G G
Messenger RNA
Transfer RNA
Nextamino acid
Ribosome
1
1
2
2
3
37
4
4
5
5
6 7
CC
C G U
6
UCG GA AA A A AG G G G G G G GC C C C C C CU U
The tRNA molecule thatbrought the last amino acidto the ribosome is releasedto the cytoplasm, and will beused again. The ribosomemoves to a new position atthe next codon on mRNA.
3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 4.24d
C CG C GU
Messenger RNA
Transfer RNA
Next amino acid
1
1
2
2
3
3
4
4
5
5
6 7
6 7
UCG GA AA A A AG G G G G G G GC C C C C C CU U
A new tRNA complementary tothe next codon on mRNA bringsthe next amino acid to be addedto the growing polypeptide chain.
4
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
AlanineAlanine
Glycine
Glycine
SerineMethionine
Step 1
Fig. 4.23c
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
C
Codon 1
Codon 2
Codon 3
Codon 4
Codon 5
Codon 6
Codon 7
G
G
G
G
G
A
A
A
U
U
C
C
C
C
C
C
G
G
G
A
Methionine
Glycine
Amino acidsrepresented
Serine
Alanine
Threonine
Alanine
Glycine
mRNA
Fig. 4.25
Code forGlutamicacid
Mutation
Dir
ecti
on
of
“rea
din
g”
cod
e
Code for valine
(a) (b)
S
S
S
C
T
A
P
P
P
S
S
S
C
T
T
P
P
P
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
A single base MutationDNA DNA
Fig. 4.26 STARTING MATERIALS
INTERMEDIATE #1
Enzyme #1
Enzyme #2
Enzyme #3
Enzyme #4
Enzyme #5
Enzyme #6
Enzyme #8
HEME
Enzyme #7
ALA dehydratase deficiency
acute intermittent porphyria
congenital erythropoietic porphyria
porphyria cutanea tarda
coproporphyria
erythropoietic protoporphyria
porphyria variegata
INTERMEDIATE #2
INTERMEDIATE #3
INTERMEDIATE #4
INTERMEDIATE #5
INTERMEDIATE #6
INTERMEDIATE #7
Resulting Conditions
Consequencesof mutations in enzymes in thesynthesis of Heme